Jaisoon Kim

Toward a miniature endomicroscope: pixelation-free and diffraction-limited imaging through a fiber bundle

A fiber bundle is widely used for endoscopic imaging due to its direct image delivery capability. However, there exists an inevitable pixelation artifact, which limits spatial resolution to the diameter of individual fibers. In this Letter, we present a method that can eliminate this artifact and achieve diffraction-limited spatial resolution. We exploited the binary control of a digital micromirror device to measure a transmission matrix of a fiber bundle and to subsequently control mode mixing among individual fibers. In doing so, we achieved a 22 kHz scanning rate of a diffraction-limited focused spot and obtained fluorescence endoscope imaging (58 μm × 58 μm) with near video-rate (10.3 Hz) acquisition. Our study lays a foundation for developing an ultrathin and high-resolution microendoscope.

Multiview Image Acquisition and Projection

A solution for describing both the multiview image set, obtained with a parallel camera layout, and the perceived image in a projection-type full parallax multiview imaging system with a parallel projector layout, is derived. This is done with the use of 4times4 homogenous matrices to quantitatively analyze the image quality in the system. The solution provides a means of finding properties and/or behavior of the perceived image changes depending on the viewers position in the system. The solution can analytically describe the appearance of three-dimensional images in the space generated by the multiview image set displayed on a projection screen

Image Light Distribution in the Multiview 3-D Imaging System

The light intensity distributions in the front space of a contact-type multiview 3-D imaging system are measured to estimate the effects of the differences in real and nominal values of parameters and alignment errors on the quality of 3-D images. The distributions clearly reveal how the viewing zone cross section is formed and how the mixed images are formed. For these measurements, a 1×4 Fresnel lens array and a projector are used as the viewing zone forming optics and image source, respectively. The results are graphically represented in terms of crosstalk. Both the misalignments and the inaccuracies greatly increase the crosstalk.

Definitive number of atoms on demand: Controlling the number of atoms in a few-atom magneto-optical trap

A few Rb85 atoms were trapped in a micron-size magneto-optical trap with a high quadrupole magnetic-field gradient and the number of atoms was precisely controlled by suppressing stochastic loading and loss events via real-time feedback on the magnetic-field gradient. The measured occupation probability of a single atom was as high as 99%. Atoms up to five were also trapped with high occupation probabilities. The present technique could be used to make a deterministic atom source.

Observation of Coiled Blood Plexus in Rat Skin with Diffusive Light Illumination

Blood plexuses are characteristic anatomical features of acupuncture points (APs). We developed an optical technique using diffusive light illumination to increase the brightened area of skin for observation of the blood plexuses in skin. We found that the blood plexuses were coiled blood vessels which came out of the perforations in the fascia of muscle. The coiled vessels could be straightened by stretching the skin. We observed a series of blood plexuses at the putative APs along the left and right kidney meridian lines in the abdominal skin of rats. In addition, the locations of the plexuses on the muscle fascia were just above the putative acupuncture muscle channels along the kidney meridians. Furthermore, immunohistochemical analysis of the skin specimens of the plexuses revealed its neurovascular bundle nature as expected from known anatomical features of the APs.

Dependence of transverse and longitudinal resolutions on incident Gaussian beam widths in the illumination part of optical scanning microscopy

We studied both theoretically and experimentally the intensity distribution of a Gaussian laser beam when it was focused by an objective lens with its numerical aperture up to 0.95. Approximate formulas for full width at half-maximum (FWHM) of the intensity distribution at focus were derived for very large and very small initial beam waists with respect to the entrance pupil radius of the objective lens. In experiments, the energy flux through a 0.5 microm pinhole was measured for various pinhole positions. It was found in theoretical analysis and confirmed in experiments that the FWHMs at focus in the transverse and longitudinal directions do not increase much from the ultimate FWHMs until the input beam waist is reduced below half of the entrance pupil radius.

Behaviors of moiré fringes induced by plate thickness

The chirped moire fringes in two superposed regularly patterned plates are investigated. When the top plate of the two superposed plates has a thickness, the periods of the moire fringes become different from that of the plate with no thickness, and the fringes shift as the viewing position changes. These variations are induced because the pattern period of the bottom plate is virtually shortened by light refraction when it is viewed through the top plate due to the top plates refractive index. The amount of shortening is small but different for different thicknesses, viewing positions and distances and lengths of the plates. Since the shortening amount is a function of the viewing angle, its variation has a chirped signal pattern. It turns the pattern with a uniform line array into a chirp-signal-type line array pattern. As a consequence, the moire fringes will be chirped, and they become more noticeable as the plate lengths increase. The simulation and experimental results are matched very closely.

Recording of High Spatial Frequency Using two Confocal Lenses in Digital Holography

The angle of an incoming laser light ray is reduced by an amount equal to the ratio of focal lengths of two confocal lenses. This lowers the spatial frequency of the interference pattern. By using an optical setup of confocal lenses, the area of the zero-order diffraction is reduced by the square of the ratio of the two focal lengths during numerical reconstruction.

Plane wave illumination for correct phase analysis and alternative phase unwrapping in dual-type (transmission and reflection) three-dimensional digital holographic microscopy

The digital holographic microscope (DHM) has emerged as a useful tool for verifying the three-dimensional structure of an object. A dual-type inline DHM that can be used with both transmission and reflection imaging in a single device is developed. The proper modes (between transmission and reflection imaging) can be easily changed according to the characteristics of the object in this system. The optimum condition for retrieving the correct phase information is illuminating a plane wave to an object. In contrast to the transmission imaging, it is difficult to illuminate an object using a plane wave without deformations in the reflection imaging. We developed an adequate relay lens module for illumination that can be adapted to any type of microscope objective without significant aberrations in the reflection imaging. The relationship between the illuminating condition and the measured phase based on the wave optics is analyzed. A specially designed and manufactured phase mask is observed in this system, and an alternative method for overcoming the limitation of phase unwrapping is introduced for the inspection of that object.

Study on elimination of twin image in a combined dual-type digital hologram microscope system

Holography has a considerable advantage to retrieve the three-dimensional (3D) information of an object from only one interference recording. For several decades, the technology of digital holography (DH), which uses numerical reconstruction as opposed to illuminating the reference beam to the hologram plate, has progressed with the assistance of improvements in 2D array detectors and computers. In this paper, a dual-type inline digital hologram microscope (DHM) system that can be used with both transmission imaging and reflection imaging in a single device is developed. The proper method depending on the modes (transmission imaging or reflection imaging) can be changed easily in this system according to the characteristics of the object. Illumination with a plane wave is the necessary condition for retrieving the correct phase information. In the case of reflection imaging, unlike in transmission imaging, a special relay lens in addition to the microscope objectives (MOs) is needed to meet the needs of this condition. However, the quality of the 3D information can deteriorate significantly due to the overlapping twin image that is inherent in holography. This study suggests an effective and convenient method for eliminating the twin image that is entangled in the reconstructed information. The proposed method does not require extra components, numerical iterations, and restrictions on the object.